In recent years, under circumstances of an increasing requirements for achieving enhanced performances of electronic equipments, a high-density integration of electronic components and further a high-density assembly of electronic components are progressed, and thus miniaturization and high-density assembly of circuit boards adopted for high density assembly application employed for the above-described electronic equipments are progressed than ever before. As solutions to the high-density assembly of such circuit board or the like, a buildup multiple-layered wiring board is often adopted (see, for example, Japanese Patent Laid-Open No. H07-106,767 (1995)).
A general buildup wiring board is formed by piling up an insulating layer composed of only a resin and having a thickness of equal to or less than 100 μm and a conductor circuit. In addition, typical method for providing joints between layers may include a laser process, a photo process and the like, in place of conventional drilling processes. These processes achieves a high-density assembly by disposing via holes having smaller diameters without any restriction, and various types of interlayer insulating materials for the buildup, which correspond to respective processes, are proposed.
Nevertheless, since the joints between the layers are provided by the fine vias in the process for forming the buildup multiple-layered interconnect board, a strength of the joint is lower, and according to the circumstances, when a thermal shock is experienced, problems such as generations of a crack and/or a disconnection due to a stress created by a difference in thermal expansion between an insulating resin and copper are occurred.
Further, a fire retardancy is often required for the applications for such buildup multiple-layered interconnect boards. Conventionally, in order to provide a fire retardancy to an epoxy resin, it is general to employ a halogen-containing fire retardant agent such as brominated epoxy and the like. However, since there is a fear that dioxin is generated from halogen-containing compounds, a use of a halogen-containing fire retardant agent is avoided under a circumstance of an intensified environmental problem in these days, and a halogen-free fire retardant system is broadly required in the industry.
[Patent Literature 1]
Japanese Patent Laid-Open No. H07-106,767 (1995)